Elizabeth City officials still don't know what caused an electrical substation to go down on Sunday, but they do know not getting it fixed soon could cost the city $120,000.

Without the substation online, the city can't use all of the generators it relies on for “peak-shaving” during periods of high electrical demand on Duke Energy Progress' system, City Manager Rich Olson explained in an interview Monday. If this month's “coincident peak” occurs before the substation is operational, the city could face $120,000 in additional demand charges, he said.

The substation, on Pritchard Street, went down shortly before 9 a.m. Sunday, leaving about of the third of the city without power for more than an hour, Olson reported. Why the substation went down is still unclear, Olson said, adding that an electrical engineer from Progressive Engineering, of Charlotte, was set to inspect the substation later on Monday.

Until the city knows why the substation failed, Olson said he doesn’t know if it will be costly to repair.

However, repair costs aren't the only concern.

While the city has redistributed the substation's load to other substations, there are 5,600 kilowatts worth of peak-shaving generators at the substation site, and those generators can only feed into that substation, Olson said.

That means that, if Duke asks the city to run the generators to offset a period of high system demand, and it can't, the city will pay more in demand charges.

Olson said a relatively mild weather forecast works in the city's favor for the next few days — but Duke's system-wide coincident peak could still occur during that time for other reasons.

If the city does have to pay the extra demand charges, it will pay them out of its electrical fund. That fund is supported by customers' payments, not property taxes.